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(No Model.) 2 Sheets- Sheet 1.

P. J. SPRAGUB 8u C. R. PRATT.

ADJUSTABLE RHEOSTAT.

110.465,218. Patented Deo.15,1891.

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(No Model.) 2 Sheets-Sheet 2. F. J. SPRAGUE 8v C. R.- PRATT.

ADJUSTABLE RHEOSTAT.

Patented Dec. 15, 1891.

- proved device.

UNITED STATES" PATENT OFFICE..

FRANK J. SPRAGUE AND CHARLES R- PRATT, OF NEV YORK, N. Y.

ADJ U STAB LIE RH EO STAT.

I SPECIFICATION forming part of Letters Patent No. 465,218, datedDecember 15, 1891.

Application tiled August 25, 1891. Serial No. 403,704. (No model.)

`funty and State of New York, have invented certain new and usefulImprovement in Adlstable Rheostats, of which the following is hrowingmore or less resistance into or out of .n electric circuit and formaking and breakng such circuit.

The main object of the invention is-to provide a device of the characterindicated having a large number of contact-plates in the switch, bymeans of which the resistance is varied, said contactplates being large,but

being so mounted that they occupy a small space, and to provide arapidly-moving c0- operating contact.

In the accompanying drawings, Figure 1 is a side view, partially insection, of the irn- Fig. 2 is a section thereof at right angles toFig. 1. Fig. 3 is a view of a modiiied form of switch, and Fig. 4 is aside view of the switch-arm.

Ris a resistance-conductor or a series of resistance-conductors, theterminal 1 of which is connected or adapted to be connected to thecircuit-wire 2.v The opposite terminal 3 is connected by wire 4 to theirst or second contact-plate 5, of which there are forty-six, numberedfrom 5 to 545 on the switch apparatus, which comprises an insulating orother Suitable body 6, preferably in the form of a hollow cylinder,having a spiral groove 7 around it from end to end. On the raised thread8 are mounted the contact-plates 5, which should be made of goodconducting material and should be quite large in order to keep down thecurrent passing between the contact-plates and the co-operating-centactper unit of surface, and in order that good contact may be obtainedwithout the necessity of pressing the contact block or device stronglyagainst the contact plates there should be a wide space between adjacentcontact-plates. By the construction described sparking and heating arereduced.

With this switch we have in practice used a current of one hundredampres and two hundred and forty volts without injurious sparking andwithout burning or welding together the contacts. The contact-blockemployed had a contact-surface of about two square inches, while thecontact-plates were about an inch and a half square, and there wereabout fifty of the contact-plates. XVe do not, however, limit ourselvesto these proportions or this number of plates.

From the stationary binding-posts between terminals 1 and 3 conductors 44', the., extend to the several spirallyarranged plates. The conductor 4will lead to the plate 5, 4 to plate 5', and so on in regular order, allthe conductors being led into the hollow cylinder and through the wallthereof to the contact-plates. It is evident that by supporting thecontact-plates on the surface of the cylindrical body and leading theconnectingwires thereto from the inside of the cylinder a compact andconvenient construction is obtained. T0 avoid confusion in the drawingsonly a few of the conductors 4 are shown. One end of the insulating-bodyis support-ed by the bracket 10 and the opposite end is supportedloosely on the end of the shaft l1, which has a bearing l2. On the shaftis a wheel 13, which may be driven by any suitable power, suchas anelectric motor or by hand. To get a quick motion of the brush,speed-gearing (indicated by wheel 13') may be used. To the shaft isrigidly iixed a hub 14, carrying a riln 15, insulated by the web 1G. Therim l5 carries one or more arms 17, which pass through slots 1S in thetraveler or nut 20. This traveler consists of an insulatingring cut at21 and engaging or tting into the spiral groove er channel 7. Thecontactplates themselves form a spiral channel, andthe groove 7 in thebody is therefore not essential. Passing through the carrier is a pin22, on which is a sleeve 23, carryinga spring 24, one end of whichpresses against the lower arm 17 and is adapted to move along said armto maintain electrical contact with it, and the other end of whichcarries a switch-contact block or spring.

A carbon block is shown in the drawings, and is preferred on account ofits conducting properties and because of the small amount of frictionwhich results from the rubbingcontact between the block and thecontactplates. The block has a curved face adapted IOO to ride along onthe spirally-arranged contact-plates and to pass on to one contact-platebefore it leaves the preceding plate.

2G is a brush connected to the circuit-wire 2 and maintaining rubbingcontact with the rim l5, and hence being electrically connected to arm17, spring 24, and brush 25. Vthile -it is preferable to make the brushthe movable member of the switch, this is not essential. Vhen the firstwire is connected to the contact -plate 5 the first contactplate 5 (notshown in Fig. l, but shown in Fig. 3) will be deadthat is, it will haveno circuit connection, so that when the switch block or brush 25 movesonto the rst contact-plate the wires 2 2 will be entirely disconnected.

The operation of the apparatusabove de-` scribed is as follows: Supposethe traveler 20,

with the parts carried thereby, to be at the right end-of the spirallygrooved or channeled body, with the block 25 resting on the lfirstcontact, the circuit 2 2 being open. wheel 13 is driven in the directionto move the block 25 toward the left, and when the block moves onto thesecond contact-plate, 2

is connected to 2 through the entire resistance between terminals l and3. As block 25 moves onto the third contact-plate, the first section ofresistance is thrown out of circuit, and as the traveler and block 25advance the other sections of the resistance are successively cut outuntil, when block 25 rests on contact 545, the wires 2 2 are connecteddi- The rectly through the switch without including any of theresistances.

As already indicated, the arrangement of contacts described enables uswhile using a large number of contact-plates for the purmay be arrangedspirally on abody of diterent form, and that the switch-brush may bedierently operated without departing from onrinvention. One suchmoditicationis shown in Figs. 3 and 4. B is a suitable hase,on

which are several contact-plates 5 5', &c., corresponding to similarplates in Fig. l. These plates are insulated from each other and arearranged in a spiral line on the base. Ordinarily a large number ofcontact-plates will be used; but for simplicity of illustration a fewonly are shown. 27 is an arm mounted on ya spindle 28, which may beturned by anyv suitable means. On the arm is a carbon or other switchblock 29, having projections 30, embracing the contact-plates. sistance,and 2 2 are the wires of the motor- R is the re-.

circuit, 2 being connected to the terminal post l and 2 being connectedto the brush 3l, bearing against the spindle 2S, which is electricallyconnected with the arm 27 and block 29. The iirst plate 5 is dead; butthe following plates are connected in regular order to the successivesections of the resistance by wires 4 4, &c., the last section beingconnected tozthe last plate 5". `When the arm 27 is moved, theswitch-block will ride alongon the successive contacts and will be movedlengthwise on the arm by the spirallyarranged contact-plates acting onthe projection 30 of the block in an evident manner.

1. The combination, in an adjustable rheostat, of a series ofcontact-plates spirally arranged and a relatively-moving switch-contactadapted to co-operate with said 'contactf plates, substantially asdescribed.

2. The combination of a suitable body, several separate contact-platesarranged spirally thereon, and a switch contact adapted to cooperatewith said spirally-arranged contacts, said contact-plates andswitch-contact moving relatively in two directions, substantially asdescribed.

3. The combination of a suitable body, several separate contact-platesarranged spirally thereon, and a switch-contact movable spi-rali y alongsaid body Aand adapted to co-operate with said spirally-arrangedcontacts, substantially as described.

4. The combination, ina switch, of a stationary body, severalcontact-plates spirally-arranged thereon and connected or adapted Vto beconnected to a circuit, and a switch-contact movable along spirally oversaid contactplates vand connected or adapted to be con` nected to acircuit, substantially as described.

IOO

5. The combination of 'a suitable body, a

series of contacts arranged spirally thereon, there being a channelbetween the turns of the spiral, and a relatively-movable switchcontactengaging or fitting into said channel so as to be moved lengthwise ofthe body, substantially as described.

6. The combination of a body havinga spiral groove or channel, contactsarranged spirally on said body, a traveler movable along the spiralgroove or channel, and a switch-contact moved by the traveler,substantially as described.

7. The combination of a stationary cylinder, contacts arranged spirallythereon,'aJ traveler carrying a switch-contact, and means Afor turningsaid carrier, whereby the switch-contact is moved along over thespirally-arranged contact, substantially as described.

8. The combination -of -a resistanceconductor, several contactsconnected therewith at different points, said contacts being mountedspirally-0n a supporting-body, and a switchcontact co-operating with theseveral spiral contacts, substantially as described.

9. The combination of a resistanccconductor, several contacts connectedtherewith IIO IIS

at dierent points, said contacts being rnounted spirally on asupporting-body, and a switchcontact movable spirally along said body inposition to co-operate with the several spiral contacts, substantiallyas described.

10. The combination of a resistance-conductor, one end of which isconnected or adapted to be connected to a circuit, and a switch forthrowing more or less of said resistanceinto or out of circuit, saidswitch consisting of a suitable body on which are several contact-platesspirally arranged, and a co-op erating switch-contact adapted to makecontact with the several spirally-arranged contacts, and a connectionfrom each of said contacts to a different point in theresistanceconductor, substantially as described.

11. The combination of a hollow cylindrical I body, a series ofspirally-arranged contactplates on the surface thereof, and wiresleading to said plates from the interior of the body, substantially asdescribed.

12. The combination, with a resistance-conductor, of a switch comprisinga hollow cylindrical body, a series of contact-plates spirally arrangedthereon, a co-operating switch-contact, and wires leading from theresistanceconductor through the cylindrical body to the contact-plates,substantially as described.

This specification signed and witnessed this 3o 11th day of August,1891.

FRANK J. SPRAGUE. CHARLES R. PRATT. Witnesses:

IRVING S. SMITH, J. C. GRIsWoLD.

npon the application of Frank J. Sprague and Charles R. Pratt, of NewYorlvr, N "for an improvement in Adjustableheostats, errors appear inthe printed sp tion requiring correction as follows: In line 46,

` the following sentence;

It is hereby eertiiied that in Letters Patent No. 465,218, grantedDecember 15, u

page 1, a semieolon should be in after the word eontaet-plates; alsoafter the saine word inline 48, same'page word By should` commence witha small b, making aconti andthat the said Letters atent'should. be readwith thesel corr therein to conform to the papers pertaining to thecasein the'Patent foe. i Y Signed, countersigned, and sealed this 29thday of v1.)eeembe13 A. D. 1891. I

- [SEAL] i 4 oYnUs BUssEY ,e V Assistant Secretary of the Interi'o'Countersiguedz W. E. SIMoNDs,

Commissioner of Patents.

4It is hereby certified that in Letters Patent No. 465,218, grantedDecember 15, 1891, y y upon the application of Frank J. Sprague andCharles R. Pratt, of New York, N. Y.,

for an improvement in Adjustable Rheostatsf7 errors appear in theprinted specification requiring correction as follows: In line 46, page1, a semicolon should be inserted after the word contact-plates, alsoafter the same word in line 48, same page, and the following Word By77should commence with a small b, making a continuous sentence; and 1thatthe said Letters Patent should be read with these corrections l thereinto conform to the papers pertaining to the case in the Patent Office.Signed, oountersigned, and sealed this 29th day of December, A. D. 1891.

[SEAL] oYRUs BUssEY,

Assistant Secretary of the Interior. Countersigned:

W. E. SIMoNDs,

Commissioner of Patents.

